This invention relates to drilling fluid additives and methods of their preparation and use thereof. More particularly, the invention relates to a drilling fluid rheology stabilizer or drilling fluid thinner and methods of their preparation and use of the same. The inventive drilling fluid additives are used as the rheology stabilizer, thinner, clay and shale stabilizer of drilling fluids in drilling and extracting petroleum, natural gas, geothermal fluids and underground water for more effectively drilling wells.
When drilling subterranean wells in order to extract petroleum, natural gas, geothermal fluids and underground water, a fluid is pumped into drill stem to be spouted out from bit nozzles. The fluid returns to the surface of the well through the annulus of the borehole, is centrifuged separation and filtered through screen, is adjusted the fluid to the desired properties, and is again pumped into drill stem. The circulated fluid is referred to as drilling fluid. The functions of the drilling fluid are: (1). to provide hydrostatic pressure to the borehole to prevent the hole from caving in or blowing out during the use of high pressure fluids: (2). to cool and lubricate the drill bit and stem; (3). to suspend the cuttings and solid particles such as barite, transport the cuttings, and clean the borehole; (4). to protect the borehole wall, prevent the landfall; and (5). to prevent the drilling fluid from flowing-off borehole and flowing the external fluid in borehole. The drilling fluids must have excellent rheology and necessary thixotropy for performing the functions of the drilling fluids.
The rheology of the drilling fluids can be expressed as apparent viscosity, plastic viscosity, yield point and gel strength. The apparent viscosity or resistance to flow of drilling fluids is the result of two properties, plastic viscosity and yield point. Each of these two properties represents a different source of resistance to flow. Plastic viscosity is a property related to the concentration of solids in the fluid, whereas yield point is a property related to the interparticle forces. Gel strength, on the other hand, is a property that denotes the thixotropy of fluid at rest.
The derivatives of lignin, derivatives of lignite, derivatives of tannin and polyphosphates are used to control the rheology and thioxotropy of drilling fluids. However, the above-mentioned additives lose their deflocculated function when temperature of drilling fluid heighten during the drilling deep wells or the concentration of contaminants such as salts increases. Polyacrylates exhibit excellent thinning and temperature stability properties, but they are sensitive to salts such as calcium salts.
The hydrophilic groups and sulfo- group [xe2x80x94SO3H] of high salts-resistance are incorporated in the synthetic materials for improving high-temperature and salts-resistance of drilling fluids. U.S. Pat. No. 3,730,900 (Alphonse C. Perricone) discloses styrene sulfonic acid-maleic anhydride copolymer as a colloidal stabilizer. U.S. Pat. No. 4,478,727 (S. Richard Turner) discloses sodium styrene sulfonate-co-N-(4-sulfophenyl)-maleimide for adjusting rheology of drilling fluids. U.S. Pat. No. 4,581,147 (Homer Branch) discloses a copolymer of sulfonated styrene and maleimide to be effective dispersant. U.S. Pat. No. 4,812,244 (Horace F. Lawson) discloses a blend of sulfonated styrene-maleimide copolymer and copolymer of acrylic acid and acrylate for improving rheology of drilling fluids.
It is necessary that drilling fluid rheology stabilizer or drilling fluid thinner adjust drilling fluid rheology when solids of drilling fluid can not be reduced because incursion and dispersion of cutting in drilling wells. The above-mentioned drilling fluid rheology stabilizers or thinners are anionic, can take apart the card house-like structure built by clay particles, adjust rheology of drilling fluid, but, reduce the drilling fluid property of inhibiting clay, result in increasing yield point, and thereby, hardly achieve low solids content of drilling fluid.
The cationic polymer clay stabilizers are prepared for inhibiting dispersion and expansion of clay. U.S. Pat. No. 4,366,072 (Homer C. HcLaughline) discloses polydimethyldiallylammonium chlorides as clay stabilizer. U.S. Pat. No. 5,160,642 (John A. Schield) discloses a quanternary ammonium salt of an imide of polymaleic anhydride as clay stabilizer. The quanternary salts can inhibit dispersion and expansion of clay, but instead, do not reduce viscosity of drilling fluids.
In order to increase calcium tolerance, some compounds are synthesized. U.S. Pat. No. 4,207,405 (William F. Masler) discloses a polymer of polymaleic anhydride and phosphorous acid. U.S. Pat. No. 4,239,648 (Alan Marshall) discloses polymer of acrylic acid and hypophosphorous acid. The polymers have very high salt-resistance, but do not reduce viscosity of drilling fluids.
The object of the present invention is to provide high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizers and methods of preparing the same. The drilling fluid rheology stabilizer or drilling fluid thinner can high-efficiently adjust rheology of drilling fluids at high-temperature high-pressure encountered in depth wells and high-mineralized degree, remarkably reduce viscosity of drilling fluid, stabilizes caly and shale, and more efficiently raise the speed of drilling well.
An object of the present invention is to provide a drilling fluid additive or drilling fluid rheology stabilizer or drilling fluid thinner.
Another object of the invention is to provide a high efficient stable rheology stabilizer or thinner of drilling fluids at high-temperature high-pressure environment encountered in drilling deep well.
Another object of the invention is to provide a high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or drilling fluid thinner.
Another object of the invention is to provide a method of producing drilling fluid rheology stabilizer or thinner for high-temperature high-pressure high-mineralized degree wells.
To achieve these objects and in accordance with the purpose of the invention, the present invention provides a high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or thinner that is a copolymer synthesized by an olefinic acid, ester of an olefinic acid, a sulfonic acid containing unsaturated linkage(s), an amide or imide containing unsaturated linkage, a quanternary compound containing olefinic linkage(s) reacting chemically with phosphorous acid or hypophosphorous acid.
In another embodiment, the present invention provides a high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or thinner that is a copolymer synthesized by acrylic acid, 2-hydroxypropyl acrylate, N-(4-sulfophenyl)-maleimide, allyltrimethyl ammonium chloride reacting chemically with phosphorous acid. The molecule of the copolymer contains 20-80 monomer units, weight average molecular weights of which are between about 3,000 to 11,800, preferably between about 3,400 to 6,000.
In another embodiment, the present invention provides a high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or thinner that is a copolymer synthesized by acrylic acid, 2-hydroxypropyl acrylate, acrylamide, 2-sulfopropyl acrylate, diallyldimethyl ammonium chloride reacting chemically with phosphorous acid. The molecule of the copolymer contains 26-90 monomer units, a weight average molecular weight of which are between about 2,600 to 11,000, preferably between abut 5,200 to 8,000.
The invention provides methods of producing the inventive high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or thinner comprising the steps of adding an olefinic acid, ester of an olefinic acid, an amide or imide containing unsaturated linkage(s), a sulfonic acid containing unsaturated linkage(s), a quanternary compound containing olefinic linkage, phosphorous acid or hypophosphorous acid to a reaction vessel charged with a special solvent, adding a polymerization catalyst, heating the reactants in the solvent to initiate polymerization reaction, maintaining a period of the reaction, adding a chain termination agent, separating the solvent from the mixture, neutralizing the solution with alkali, and spray-drying with a spray-drying instrument to yield the powder product.
The present invention provides a high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or a drilling fluid thinner comprising a copolymer synthesized by an olefinic acid, ester of an olefinic acid, a sulfonic acid containing unsaturated linkage(s), an amide or imide containing unsaturated linkage(s), a quanternary compound containing olefinic linkage(s) reacting chemically with one of either phosphorous acid or hypophosphorous acid, having the following formula:
[M]m[N]n[P]p[Q]q[R]r[A]a
wherein M, N, P, Q, R, A respectively represent monomer units derived from an olefinic acid, ester of an olefinic acid, a sulfonic acid containing unsaturated linkage(s), an amide or imide containing unsaturated linkage(s), a quanternary compound containing olefinic linkage(s), one of either phosphorous acid or hypophosphorous acid in the molecule of the copolymer; m, n, p, q, r and a respectively represent number of the olefinic acid, ester of the olefinic acid, the sulfonic acid containing unsaturated linkage(s), the amide or imide containing unsaturated linkage(s), the quanternary compound containing olefinic linkage(s), the phosphorous acid or hypophosphorous acid monomer units in the moleucle of the copolymer; M, N, P, Q, R, A are connected in any sequences in the molecule of the copolymer. The said olefinic acid includes acrylic acid and methacrylic acid; the ester of the olefinic acid includes 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl methacrylate and 2-hydroxyethyl methacrylate; the amide or imide containing unsaturated linkage(s) includes acrylamide and methacrylamide; the sulfonic acid containing unsaturated linkage(s) includes 2-sulfopropyl acrylate, 2-sulfoethyl acrylate, 2-sulfopropyl methacrylate, 2-sulfoethyl methacrylate, N-(4-sulfophenyl)-maleimide; the quanternary compound containing olefinic linkage(s) includes allyltrimethylammonium chloride, allyltrimethyl ammonium bromide, allyltrimethylammonium iodide, allyltrimethylammonium bicarbonate, diallyldimethylammonium chloride, diallyldimethylammonium bromide, diallyldimethylammonium iodide, diallyldimethylammonium bicarbonate; the said phosphorous acid or hypophosphorous acid includes phosphorous acid, sodium phosphite, potassium phosphite, ammonium phosphite, hypophosphorous acid, sodium hypophosphite, potassium hypophosphite, ammonium hypophosphite. It is critical that the polymer includes at least two kinds of monomer units, provided that it at least a contains quanternary group, a phosphino group, a carboxyl group, a sulfo-group, and one of either amido or imido group.
In another embodiment, the present invention provides a high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or thinner that is a copolymer synthesized by acrylic acid, 2-hydroxypropyl acrylate, N-(4-sulfophenyl)-maleimide, allyltrimethyl ammonium chloride reacting chemically with phosphorous acid; the molecule of the copolymer has from 20 to 80 monomer units in order to adjust effectively rheology of drilling fluid. The copolymer has the formula: 
wherein X and Y are independently selected from the group consisting of H, Na, K, NH4; Z is selected from the group consisting of Cl, Br, I, HCO3; m=6-18, preferably m=8-12; n=3-10, preferably n=2-6; p=6-22, preferably p=8-12; q=3-20, preferably q=4-6, wherein m:n:p:q=(6-18):(3-10): (6-22): (3-20), preferably (8-12):(2-6):(8-12):(4-6), mole ratio of a: (m+n+p+q) is 1:7, preferably 1:6, weight average molecular weights of the copolymer are 3,000-11,800, preferably 3,400-6,000. The above monomer units are in any positions in molecule of the copolymer.
In another embodiment, the present invention provides a high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or thinner copolymer synthesized by acrylic acid, acrylamide, 2-hydroxypropyl acrylate, 2-sulfopropyl acrylate, diallyldimethylammonium chloride reacting chemically with phosphorous acid; the molecule of the copolymer has from 26 to 90 monomer units. The monomer units are in any positions in molecule of the copolymer. The copolymer has the formula. 
wherein X and Y are independently selected from the group consisting of H, Na, K, NH4; Z is selected from the group consisting of Cl, Br, I, HCO3; m=8-21, preferably m=10-16; n=3-10, preferably n=5-6, s=8-20, preferably s=12-13; t=1-10, preferably t=3-6; r=6-22, preferably r=8-18; wherein mole ratio of m:n:s:t:r is (8-21):(3-10):(8-20):(1-10):(6-22), preferably (10-16):(5-6):(12-13):(3-6):(8-18); b:(m+n+s+t+r)=1:7, preferably 2:9; weight average molecular weights of the copolymer are 2,600-11,000, preferably 5,200-8,000.
The present invention provides methods of preparing high-temperature high-pressure high-mineralized degree drilling fluid rheology stabilizer or thinner. The methods comprise the steps of adding reactants of the olefinic acid, the amide or imide containing unsaturated linkage(s), the ester of the olefinic acid, the sulfonic acid containing unsaturated linkage(s), the quanternary compound containing olefinic linkage(s), phosphorous acid or hypophosphorous acid to a reaction vessel charged with the solvent, adding the polymerization catalyst, heating the materials in the reaction vessel to such temperature that the polymerization is initiated, maintaining a period of the reaction at the said temperature, adding the chain termination agent, separating the solvent from the mixture, neutralizing the solution with alkali, spray-drying the solution to powder product using a spray-drying instrument. The said solvent is inert to the reactants and is selected from 1,2-dichloroethane, 1,1,1-trichloroethane, benzene, xylene, n-hexane, carbontetrachloride and water; the polymerization catalysts is selected from free radical initiators or redox initiators such as benzoyl peroxide, lauryl peroxide, hydrogen peroxide, sodium persulfate, ammonium persulfate in order to prompt the polymerization; chain termination agent is selected from mercaptan, benzyl alcohol, benzaldehyde and thioglycolic acid; the content of reactants is 10-100 wt % based on the total weight of the solution of the reactants in said solvent, preferably 30-50wt %; amount of the catalyst to be added is 0.1-20wt % based on the weight of the total reactants, preferably 1-3wt %; the reactive temperature is 10-200xc2x0 C., preferably 50-110xc2x0 C.; the reactive time is 10 seconds to 10 hours, preferably 2-3 hours; the said alkali is sodium hydroxide, potassium hydroxide, ammonium hydroxide; the solution is neutralized to pH3-13, preferably pH8-11; temperature of inlet of the spray-drying instrument is 150-500xc2x0 C., preferably 200-300xc2x0 C., outlet 40-120xc2x0 C., preferably 60-90xc2x0 C.; particle size of the product is 10-160 mesh, preferably 30-60 mesh.
In methods of preparing the inventive drilling fluid rheology stabilizer, the operational procedures are selected independently as follows: (1) adding reactants in accordance with the any sequences, heating to initiative temperature, adding the polymerization catalyst and adding the chain termination agent; (2) adding the reactants and the chain termination agent, heating to initiative temperature, adding the polymerization catalyst; (3) adding the olefinic acid, the ester of olefinic acid, the amide or imide containing unsaturated linkage(s), sulfonic acid containing unsaturated linkage(s), the quanternary compound containing olefinic linkage, the polymerization catalyst, maintaining reaction temperature and time, and adding phosphorous acid or hypophosphorous acid, adding chain termination agent; (4) adding the olefinic acid, the ester of the olefinic acid, the amide or imide containing unsaturated linkage(s), the sulfonic acid containing unsaturated linkage(s), the quanternary compound containing olefinic linkage, the polymerization catalyst, the chain termination agent, maintaining the reaction temperature and time, and adding phosphorous acid or hypophosphorous acid.